Adjustable Cutting Mill Assembly and Methods of Operation

ABSTRACT

A system and method for adjusting or controlling at least one milling operating feature of a cutting mill assembly within a wellbore includes sensing at least one milling operating parameter with a sensor that is operably associated with the cutting mill assembly that is run into the wellbore. At least one milling operating feature of the cutting mill assembly is adjusted or controlled in response to the at least one milling operating parameter that is sensed.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates generally to downhole cutting mills and methodsfor operation of such cutting mills.

2. Description of the Related Art

Milling tools, or mills, are used to perform cutting tasks within asubterranean wellbore. As opposed to drill bits, which tunnel throughthe earth, mills are often employed to cut away discrete objects withinor associated with a wellbore. For example, a cutting mill is used tocut through a plug or other obstruction which is located within the boreof a well. A casing exit mill is used to cut a window in metallicwellbore casing.

SUMMARY OF THE INVENTION

The present invention relates to cutting mill assemblies which areadjustable in at least one of several ways to alter the cutting abilityor nature of the cutting mill during operation. The invention featuresmethods for operating a cutting mill assembly wherein one or moremilling operating parameters are sensed or measured and, in response, amilling operating feature associated with the cutting mill or itsoperation is adjusted.

Exemplary milling operating parameters which can be sensed includetorque experienced by the milling bottom hole assembly, weight-on-bit,flow rate at surface, flow rate proximate the bottom hole assembly,temperature, pressure and vibration. In preferred embodiments, suitablesensors are provided within the cutting mill assembly to detect andmeasure these milling operating parameters and to provide generatedsignals indicative of each.

In described embodiments, the milling operating features which areadjusted include movement of, including the amount of protrusion of, acutter from the cutting mill body, diameter of the cutting mill body andfluid flow through a nozzle on the cutting mill body. Other adjustablemilling operating features include vibration imparted to the cuttingmill bottom hole assembly and the rate of fluid flow provided to thecutting mill bottom hole assembly.

In described embodiments, a controller is provided which is capable ofreceiving signals representative of the sensed milling operatingparameters as well as providing control commands to adjust a millingoperating feature. In certain embodiments, the controller senses one ormore milling parameters and adjusts one or more milling operatingfeatures autonomously.

In described embodiments, an adjustable cutting mill features a millbody with a plurality of cutters, at least one or more of which aremoveable with respect to the mill body. Movement of the one or morecutters is a milling operating feature which can be adjusted in responseto sensed milling parameters. The one or more cutters are adjustable bymovement to cause the cutter(s) to protrude outwardly from the mill bodyto a greater extent or lesser extent. In described embodiments,mechanisms are provided for moving the cutters with respect to the millbody. In preferred embodiments, the cutters can be remotely adjustedwith respect to the mill body. In still other embodiments, the cutter(s)are autonomously adjusted with respect to the mill body by a controllerbased upon sensed downhole and/or uphole milling operating parameters.

In certain embodiments, an adjustable cutting mill is provided whichincludes a mill body having an adjustable diameter. In particular, wedgeportions of the mill body can be moved to alter the diameter of the millbody. The diameter of the mill body is a milling operating feature whichcan be adjusted in response to sensed milling parameters. The diameterof the mill body might be reduced in response to detection of sensedmilling parameters which indicate a restriction in the wellbore andwherein reduction of the mill body diameter would permit the mill bodyto pass through the restriction.

In other aspects, the cutting mill assembly includes nozzles or flowports that are adjustable in flow area. Flow area can be adjusted toallow greater flow of fluid or lesser flow of fluid. This would alsoaffect the pressure at which fluid exits the nozzle or flow port. Nozzleflow area is also a milling operating feature which can be adjusted orcontrolled in response to one or more sensed milling operatingparameters.

In certain embodiments, the cutting mill assembly includes an extendedreach tool which imparts vibration to the tool string to improve cuttingability at desired depth of the well. In described embodiments, theextended reach tool is operably associated with the controller so thatvibrational energy can be created by the extended reach tool to increasethe cutting effectiveness of the milling bottom hole assembly. Vibrationcreated by the extended reach tool is a milling operating feature whichcan be adjusted or controlled in response to sensed milling operatingparameters.

In described embodiments, the cutting mill assembly includes acirculation tool that includes lateral ports which can be opened toadjust fluid flow to the milling bottom hole assembly. Fluid flow to themilling bottom hole assembly is a milling operating feature which can beadjusted in response to sensed milling operating parameters.

In particular embodiments, a cutting mill assembly is provided whichincludes an adjustable cutting mill which is carried by a bottom holeassembly having a sensing and control unit. The sensing and control unitincludes one or more sensors which are configured to detect one or moredownhole milling parameters. In currently preferred embodiments, thedownhole milling parameters include weight on bit (WOB), torque andtemperature. Measured surface milling parameters include pump rate orfluid flow rate and surface weight of the entire cutting mill assembly.

The sensing and control unit preferably includes a controller whichreceives signals from the sensors which are representative of the one ormore milling operating parameters and is configured to determine whetheran adjustment of one or more milling operating features of the cuttingmill assembly is desired. The controller is operably associated with thecutting mill assembly so that the controller can adjust one or more ofthese features to alter the milling operation. The controller ispreferably a programmable processor with associated memory.

In a described embodiment, the bottom hole assembly of the cutting millassembly includes a communications module which permits communication ofdata and commands between the downhole controller and the surface. Thecommunication module will permit data representative of sensed millingoperating parameters to be displayed to an operator at surface. Anoperator would be able to command the controller to control or adjustone or more milling operating features.

The invention provides methods for adjusting or controlling at least onemilling operating feature of a cutting mill assembly within a wellbore.In accordance with described methods, one or more milling operatingparameters are sensed and, in response, one or more milling operatingfeatures are adjusted or controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is madeto the following detailed description of the preferred embodiments,taken in conjunction with the accompanying drawings, wherein likereference numerals designate like or similar elements throughout theseveral figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of an exemplary cutting millassembly constructed in accordance with the present invention anddisposed within a wellbore to mill away a plug.

FIG. 2 is a side view of an exemplary sensing and control module inaccordance with the present invention.

FIG. 3 is a side, cross-sectional view of an exemplary milling bithaving adjustable cutters.

FIG. 4 is a side, cross-sectional view of a portion of an exemplarymilling bit having a nozzle with adjustable flow area.

FIG. 5 is a side view illustrating an exemplary milling bit having anadjustable diameter.

FIG. 5a is a side view of the milling bit of FIG. 5, now with the millcutting diameter decreased.

FIG. 6 is a schematic view illustrating interconnection of a controllerwith a plurality of sensors for sensing milling operating parameters anda plurality of milling operating features.

FIG. 7 is a flow diagram depicting an exemplary process for adjustingcutting mill operation features in response to sensed milling operatingparameters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an exemplary wellbore 10 which has been drilled intothe earth 12 from surface 14. The wellbore 10 is lined with metalliccasing 16, of a type known in the art. A plug 18 or other obstruction ispresent in the wellbore 10, and it is desired to remove the plug 18 bycutting it away.

A cutting mill assembly 20 is disposed within the wellbore 10, havingbeen run in from the surface 14. The cutting mill assembly 20 is beingused to cut away the plug 18. Generally, the cutting mill assembly 20includes a running string 22 and a milling bottom hole assembly 24 whichis carried by the running string 22. The running string 22 is typicallycoiled tubing. However, the running string 22 might also be composed ofconventional drill pipe sections which are interconnected in end-to-endfashion, as is known in the art. A central flow bore 26 is definedwithin the running string 22 and permits flow of fluid, such as drillingmud through the running string 22 to the milling bottom hole assembly24.

In preferred embodiments, the running string 22 incorporates an extendedreach tool 28 and/or a circulation tool 30. The extended reach tool 28may be an EasyReach Extended Reach Tool which is available commerciallyfrom Baker Hughes, a GE company, LLC of Houston, Tex. The extended reachtool 28 uses water hammer effect to generate traction forces which helpto pull the running string 22 into the wellbore 10. The extended reachtool 28 is capable of imparting vibration to the milling bottom holeassembly 24, thereby increasing its rate of penetration andeffectiveness.

The circulation tool 30 is a tool which enables mid-running stringcirculation from the flow bore 26 into the annulus 32, which is definedradially between the cutting mill assembly 22 and the casing 16. Thecirculation tool 30 generally includes a generally cylindrical housing34 which defines a central flow passage 36 within. A plurality oflateral flow ports 38 are formed within the housing 34 permitting fluidflow between the annulus 32 and the flow passage 36. An interior sleeve40 is retained with in the housing 34 and can be axially shifted withinthe body 34 selectively block or unblock the ports 38. The lateral flowports 38 of the circulation tool 30 can therefore be opened, to reducefluid flow to the milling bottom hole assembly 24 through the runningstring 22, or closed, to increase fluid flow to the milling bottom holeassembly 24 through the running string 22. The circulating tool 30 ispreferably provided with a suitable solenoid valve (not shown) which isconnected with a flow channel and will enable sleeve 40 to be shiftedvia fluid pressure so that the solenoid valve, under control of acontroller, will open or close the flow ports 38.

A surface weight scale, of a type known in the art, is shownschematically at 42 in FIG. 1. Typically, the surface weight scale 42 isincorporated into the suspension and drawworks for the cutting millassembly 20 and will measure the entire weight of the cutting millassembly 20 when it is suspended within the wellbore 10. The measuredweight is referred to as the weight measured at surface or the “surfaceweight.” The weight scale 42 generates an electronic signal which isindicative of the measured surface weight.

Now also referring to FIG. 3 as well as FIG. 1, the milling bottom holeassembly 24 includes a milling bit 44 having a mill body 46 and aplurality of hardened cutters 48 which are mounted thereupon. The millbody 46 also includes a plurality of nozzles 50 through which fluid,which is pumped from the surface 14 through the running string 22 willexit the mill body 46 during milling. The milling bit 44 is rotated bymotor 52 during operation. The motor 52 may be a hydraulically-drivenmotor of a type known in the art. A fluid pump 54 is located at surface14 and is operably associated with the running string 22 to flowdrilling fluid through the running string 22. A flow meter 56 isoperably associated with the fluid pump 54 in order to measure the pumprate or fluid flow rate of drilling fluid entering the running string22.

It is noted that the milling tool which is being described is a cuttingmill that is used to cut away a plug or obstruction within a wellbore.It should be understood, however, that other forms of milling tools canbe used as well. For example, the milling tool could be a casing exitmill which is used to cut an opening within the wellbore casing 16.

The milling bottom hole assembly 24 also includes a sensing and controlmodule 58, which is illustrated in greater detail in FIG. 2. The sensingand control module 58 includes at least one sensor 60 which is operableto detect at least one downhole milling operating parameter. In thedepicted embodiment, there are multiple sensors 60 which are positionedon the outer surface 62 of the module housing 64 of the sensing andcontrol module 58. Exemplary downhole milling operating parameters whichare sensed include weight on bit (WOB), torque, pressure, temperature,vibration and flow rate of fluid received from the running string 22proximate the milling bottom hole assembly 24. The sensing and controlmodule 58 also includes a controller 66 which receives signals from thesensor(s) 60 which are indicative of the sensed downhole millingoperating parameter(s). In addition, and as illustrated in FIG. 6, thecontroller 66 preferably receives signals indicative of fluid flow intothe running string 22 from flow meter 56 at surface 14 as well as thecutting mill assembly 20 weight from weight scale 42 also at surface 14.Thus, the controller 66 receives signals representative of the downholesensed milling operating parameters (from sensors 60) as well as upholemilling parameters (from flow meter 56 and scale 42).

The controller 66 may be in the form of one or more printed circuitboards which contain a programmable processor, data storage and thenecessary computer programming to receive signals from the sensors 60which are indicative of sensed downhole milling operating parameters andcalculate desired adjustments for adjustable milling operating features.Data connections 68 transmit signals from the sensors 60 to thecontroller 66. As shown in FIG. 2, the sensing and control module 58includes a central axial fluid flow path 70 which allows fluid pumpedfrom surface 14 to be flowed to the milling bit 44.

The controller 66 is also operably interconnected with certainadjustable milling operating features of the cutting mill assembly 20 inorder to control those milling operating features. Control line 72extends from the controller 66 to the milling bit 44. The control line72 carries actuation commands from the controller 66 to adjust theextension of mill bit cutters 48 or flow rate through nozzles 50, aswill be described.

Referring once again to FIG. 3, an exemplary milling bit 44 is shownwhich has adjustable milling operating features. The depicted millingbit 44 is preferably an end mill or junk mill which is used to removeobstructions within a wellbore 10. Except where otherwise described, themilling bit 44 may be constructed and operate in the same manner as theMetal Muncher™ junk mill which is available commercially from BakerHughes, a GE company, LLC of Houston, Tex. The bit body 46 of millingbit 44 includes a threaded connection 74 for attaching the milling bit44 to neighboring components in the cutting mill bottom hole assembly24. A central axial flow bore 76 extends through the bit body 46. Thebit body 46 presents a lower cutting face 78 upon which cutters 48 aremounted. At least one of the cutters 48 are adjustable such that theycan be extended or retracted from a recess 80 in the cutting face 78. InFIG. 3, only a single cutter 48 is illustrated as being adjustable inthis manner. It should be understood, however, that multiple cutters 48or even all of the cutters 48 may be adjustable. Fluid nozzle 50 is influid communication with the flow bore 76 so that fluid flowed throughthe flow bore 76 can exit through the cutting face 78 during operation.

The milling bit 44 includes an actuator, generally indicated at 82, forextending or retracting cutter 48 from recess 80. The actuator 82includes a motorized fluid pump 84 which is operably interconnected withthe control line 72 so that the pump 84 can be actuated by thecontroller 66. The actuator 82 also includes a piston chamber 86 whichis in fluid communication with the pump 84. Piston 88 resides within thepiston chamber 86 and is moveable within the chamber 86. Rod 90 securesthe piston 88 to cutter 48. The actuator 82 can move the cutter 48between a retracted position, wherein the cutter 48 is fully containedwithin the recess 80 and an alternate, extended position indicated at 48a. When the controller 66 commands the pump 84 to flow fluid to thechamber 86, the piston 88 is moved to the alternate, extended position48 a. When the controller 66 commands the pump 84 to flow fluid out ofthe chamber 86, the cutter 48 is returned to the retracted positionwithin the recess 80. Other techniques and mechanisms for extending andretracting cutters are described in U.S. Pat. Publication No.2015/0053551 which is owned by the applicant and is herein incorporatedby reference in its entirety.

FIG. 4 schematically depicts a portion of a milling bit 44 is whichfluid passageway 88 within bit body 46 transmits fluid from the centralaxial flow bore 76 to nozzle 50. The fluid passageway 88 includes avalve seat 90. Poppet valve member 92 is located within the fluidpassageway 88 and is shaped and sized to contact the valve seat 90 toclose off or substantially limit fluid flow through the fluid passageway88 toward the nozzle 50. A linear actuator 92 controls the axialposition of the poppet valve member 92 within the fluid passageway 88.By moving the poppet valve member 92 closer to the valve seat 90, theflow of fluid to the nozzle 50 is restricted as flow area is reduced.The reduction in flow area will impact the velocity at which fluid exitsthe nozzle 50. Conversely, by moving the poppet valve member 92 furtheraway from the valve seat 90, the flow of fluid to the nozzle 50 isincreased as flow area is increased. The linear actuator 92 is operablyinterconnected with the control line 72 so that the controller 66 cancontrol the position of the poppet valve member 92.

FIGS. 5 and 5A depict an exemplary mill bit 44′ which features anadjustable mill bit body 46′. For ease and clarity of description, theadjustable features of mill bit 44′ are being described separately fromthose of mill bit 44. However, those of skill in the art will recognizethat the adjustable features of mill bit 44′ may be combined with theadjustable features of mill bit 44 in a single bit. The mill bit body46′ presents a lower cutting face 78 which has cutters formed thereuponas described previously. The mill bit body 46′ also has lateral cuttingportions 94 having hardened cutters 96 disposed therein. The lateralcutting portions 94 are adjustable by movement of a mechanical linkage98 which extends through the mill body 46′ from a control interface 100to each lateral cutting portion 94. A motor/pump 102 and sliding sleeve104 interact with the interface 100 to cause movement of the linkage 98to move the lateral cutting portions 94 between radially expanded (FIG.5) and radially contracted (FIG. 5A) positions. The motor/pump 102 isoperably interconnected with the controller 66 via control line 72. Theinterface 100 and linkage 98 function to convert the axial motion of thesliding sleeve 104 to radial angular motion for the cutting portions 94.As a result, the controller 66 will be able to provide commands to themotor/pump 102 which will result in the lateral cutting portions 94being either radially expanded or radially contracted. Movement of thelateral cutting portions 94 to a radially expanded position will providean increased diameter for the mill bit 44′. Conversely, movement of thelateral cutting portions 94 to the radially contracted position willprovide a decreased diameter for the mill bit 44′. It should beunderstood by those of skill in the art that the ability to changes thediameter of the mill body 46′ is a milling operating feature which canbe adjusted or controlled in response to sensed milling operatingparameters. Among the sensed milling operating parameters which mightresult in adjustment of the diameter of the mill body 46′ is a sensedrestriction in wellbore 10 wherein a reduction in the diameter of themill body 46′ would allow the mill body 46′ to pass through therestriction.

FIG. 6 is a schematic diagram which illustrates an exemplary operableinterconnection between the controller 66 and sensors 60 which detectseveral milling operating parameters as well as between the controller66 and a number of milling operating features which are controlled oradjusted in response to the detected milling operating parameters.Controller 66 is operably interconnected with sensors 60 which detectdownhole milling operating parameters. In addition, the controller 66 isoperably interconnected with the weight scale 42 and the flow meter 56which detect uphole milling operating parameters and provide signalsindicative of the detected parameters to the controller 66.

The controller 66 is also operably interconnected with various featureswithin the cutting mill assembly 20 which enable it to adjust or controlmilling operating features. In particular embodiments, the controller 66is operably interconnected with fluid pump 84 via control line 72 forcontrol of extension of cutters 48. Preferably, the controller 66 isalso operably interconnected via the control line 72 with linearactuator 92 in order to control or adjust flow through nozzle 50.Preferably also, the controller 66 is operably associated with themotor/pump 102 in order to control or adjust the diameter of the millbit body 46′.

As FIG. 6 depicts, the controller 66 is preferably also operablyassociated with the extended reach tool 28 in order to energize the tool28 for vibration of the cutting mill assembly 22. Energizing theextended reach tool 28 creates vibrational energy which is imparted tothe milling bottom hole assembly 24 to increase its cuttingeffectiveness. The controller 66 is preferably also operably associatedwith the circulating tool 30. The controller 66 can control thecirculating tool 30 by shifting the sleeve 40 within its housing 34 inorder to open or close the lateral flow ports 38. By doing so, thecontroller 66 can rapidly adjust the flow of fluid which is provided tothe milling bottom hole assembly 24.

In some embodiments, the controller 66 will determine what, if any,adjustments of the milling operating features need to be made. In otherembodiments, decisions about adjustment of milling operating featuresare made at surface 14 by human operators. Communications module 110(FIG. 1) is interconnected with the controller 66 by data linkage 112.The communications module 110 transmits data to a display 114 at surface14 via communication line 116 which is preferably a two-way telemetryarrangement. The display 114 displays data indicative of the at leastone milling operating parameter sensed by the sensors 60, weight scale42 and flow meter 56. An operator at surface 14 can then evaluate thedata and transmit one or more commands to the controller 66 viacommunications line 116 and data linkage 112. In response, thecontroller 66 will control the one or more adjustable features of themilling bit 44. Additionally, the communication line 116 transmitssignals representative of measured pump rate or fluid flow rate from theflow meter 56 to the controller 66 via data linkage 112. The surfaceweight scale 42 is also operably interconnected with the communicationsline 116 so that signals representative of the surface weight can beprovided to the controller 66 via the communication line 116 and datalinkage 112.

In operation, the cutting mill assembly 20 is run into the wellbore 10until the milling bottom hole assembly 24 is proximate the plug 18 to beremoved. Drilling fluid is flowed down through the cutting mill assembly20 and out through the nozzles 50 of the milling bit 44. The milling bit44 is rotated to mill away the plug 18. During milling, the sensors 60detect downhole milling operating parameters, including torque,weight-on-bit, pressure, temperature, vibration and flow rate of fluidreceived proximate the milling bottom hole assembly 24. Signalsindicative of the sensed milling operating parameters are transmittedfrom the sensors 60 to the controller 66. Other sensed millingparameters, such as pump flow rate and surface weight are transmitted tothe controller 66 from weight scale 42 and flow meter 56 at the surface14. The controller 66 then controls the adjustable milling operatingfeatures to respond to the sensed milling operating parameters.

FIG. 7 illustrates an exemplary control process 120 which might beconducted by the controller 66 or by an operator at surface 14 in orderto adjust milling operating features in response to sensed millingoperating parameters. It is noted that the depicted control process isexemplary only and no limitation to the particular described steps isintended. Rather, the steps of the control process will vary dependingupon the specific programming of the controller 66 and the capabilitiesof the individual devices which are being controlled by the controller66. In step 122, the sensors 36 measure milling operating parameters,which may include torque, vibration, temperature, pressure andweight-on-bit. In addition, the controller 66 preferably also measuressurface milling operating parameters of surface weight and fluid flowrate are measured by the surface weight scale 42 and the flow meter 56,respectively. In step 124, the sensors 60 detect excessive torque as amilling operating parameter. In step 126, the controller 66, in responseto the detection of excessive torque, then compares each of the millingparameters of downhole fluid flow rate, weight-on-bit and vibrationagainst predetermined limits. The controller 66 (or individual atsurface 14) then determines which milling operating feature to adjustbased upon the comparisons. If the measured downhole flow rate isexcessive, but weight-on-bit is acceptable (branch 128), the circulationtool 30 is actuated to reduce flow rate to the milling bottom holeassembly 24 (step 130). As a result, milling torque is reduced but holecleaning is maintained (see 132). If measured downhole flow rate isacceptable but weight-on-bit is excessive (branch 134), the controller66 (or individual at surface 14) then compares measured surface weightto downhole weight-on-bit (step 136). If surface weight is acceptable,the controller 66 (or individual at surface 14) determines (step 138)that a weight transfer issue is the cause of the excessiveweight-on-bit. In response, the controller 66 will control the extendedreach tool 28 to adjust weight-on-bit (step 140). If, during step 136,the controller 66 or individual at surface 14 determines that surfaceweight is too great (branch 142), then surface weight is reduced in step144. Surface weight adjustment is normally made by an operator atsurface 14 by adjustment of a coiled tubing injector.

If the controller 66 (or individual at surface 14) determines that theflow rate and the weight-on-bit are acceptable (branch 146), thedecision is made to adjust mill aggressiveness (step 148). Thecontroller 66/individual at surface 14 then determines whether theinteraction between the mill bit 44 and the plug 18 is excessive or not(step 150). If yes, one or more of the cutters 48 on the lower cuttingface 78 of the mill bit 46 are retracted to in step 152 in order toreduce frictional cutting contact between the mill bit 46 and the plug18. Conversely, if the interaction between the mill bit 46 and plug 18is too low, one or more cutters 48 are extended from the lower cuttingface 78 of the mill bit 46 to compensate.

The controller 66 (or individual at surface 14) can also determinewhether interaction between the mill body 46′ and the surroundingwellbore 10 is too great, which would indicate a need to reduce thediameter of the milling bit 46′. One technique for determining whetherinteraction between the mill body 46′ and surrounding wellbore 10 is toogreat is to move the tool string up and down in the wellbore 10 andmonitor weight transfer. In step 154, it is determined that contactbetween the mill body 46′ and the surrounding wellbore 10 is excessive.In response, the controller (or individual at surface 14) controls themilling bit 44′ to retract the lateral cutting portions 94 (step 156).

In accordance with the exemplary control process 120, the controller 66or individual at surface 14 can determine whether it is necessary toadjust flow rate through the nozzles 50 of the milling bit 44. In step158, it is determined that there is excessive debris around the millingbit 44. Ultrasonic imaging technology could be used to detect the amountof debris. In response, the flow area through nozzle(s) 50 is adjustedto increase flow through the nozzle 50 (step 160). These actions shouldresult in good torque response.

What is claimed is:
 1. A cutting mill assembly for performing a cuttingoperation within a wellbore, the cutting mill assembly comprising: amilling bottom hole assembly to be disposed into the wellbore by arunning string; a running string; a sensor to detect at least onemilling operating parameter; a controller which is operablyinterconnected with the sensor to receive a signal representative of themilling operating parameter; the cutting mill assembly having at leastone milling operating feature which can be adjusted; and the controllerfurther being configured to adjust or control the at least one millingoperating feature in response to the at least one milling operatingparameter.
 2. The cutting mill assembly of claim 1 wherein the at leastone milling operating feature is from the group consisting of: extensionof a cutter from a bit body of the milling bit, flow area of a nozzle inthe bit body, milling body diameter, fluid flow to the milling bottomhole assembly through the running string and vibration imparted to themilling bottom hole assembly.
 3. The cutting mill assembly of claim 1wherein the at least one milling operating parameter includes torque,weight on bit, surface weight, temperature, pressure, vibration or fluidflow received proximate the milling bit bottom hole assembly.
 4. Thecutting mill assembly of claim 1 wherein the controller is locatedwithin the milling bottom hole assembly.
 5. The cutting mill assembly ofclaim 1 wherein the controller is operably interconnected with a displayat a surface location which displays data indicative of the at least onemilling operating parameter sensed by the sensor; and wherein anoperator at a surface location can command the controller to adjust amilling operating feature of the cutting mill assembly in response tothe at least one milling operating parameter.
 6. The cutting millassembly of claim 1 wherein the controller autonomously adjusts amilling operating feature of the cutting mill assembly in response tothe at least one milling operating parameter.
 7. The cutting millassembly of claim 2 wherein the milling operating feature of vibrationimparted to the milling bottom hole assembly is adjusted or controlledby actuating an extended reach tool which is incorporated into thecutting mill assembly in order to create vibrational energy.
 8. Thecutting mill assembly of claim 2 wherein the milling operating featureof fluid flow to the milling bottom hole assembly through the runningstring is adjusted or controlled by actuating a circulation tool whichis incorporated into the cutting mill assembly.
 9. The cutting millassembly of claim 2 wherein the milling operating feature of millingbody diameter is adjusted or controlled by extending or retractinglateral cutting portions of a mill body.
 10. A cutting mill assembly forperforming a cutting operation within a wellbore, the cutting millassembly comprising: a milling bottom hole assembly to be disposed intothe wellbore by a running string; a running string; a sensor to detectat least one milling operating parameter; a controller which isincorporated into the milling bottom hole assembly and is operablyinterconnected with the sensor to receive a signal representative of themilling operating parameter; the cutting mill assembly having at leastone milling operating feature which can be adjusted; and the controllerfurther being configured to adjust or control the at least one millingoperating feature in response to the at least one milling operatingparameter.
 11. The cutting mill assembly of claim 10 wherein the atleast one milling operating feature is from the group consisting of:extension of a cutter from a bit body of the milling bit, flow area of anozzle in the bit body, milling body diameter, fluid flow to the millingbottom hole assembly through the running string and vibration impartedto the milling bottom hole assembly.
 12. The cutting mill assembly ofclaim 10 wherein the at least one milling operating parameter includestorque, weight on bit, surface weight, temperature, pressure, vibrationor fluid flow received proximate the milling bit bottom hole assembly.13. The cutting mill assembly of claim 10 wherein the controllerautonomously adjusts a milling operating feature of the cutting millassembly in response to the at least one milling operating parameter.14. The cutting mill assembly of claim 1 wherein the controller isoperably interconnected with a display at a surface location whichdisplays data indicative of the at least one milling operating parametersensed by the sensor; and wherein an operator at a surface location cancommand the controller to adjust a milling operating feature of thecutting mill assembly in response to the at least one milling operatingparameter.
 15. A method of adjusting or controlling at least one millingoperating feature of a cutting mill assembly within a wellbore, themethod comprising the steps of: sensing at least one milling operatingparameter with a sensor that is operably associated with the cuttingmill assembly that is run into the wellbore; and adjusting orcontrolling the at least one milling operating feature of the cuttingmill assembly in response to the at least one milling operatingparameter that is sensed.
 16. The method of claim 15 wherein the atleast one milling operating feature is from the group consisting of:extension of a cutter from a bit body of the milling bit, flow area of anozzle in the bit body, milling body diameter, fluid flow to the millingbottom hole assembly through the running string and vibration impartedto the milling bottom hole assembly.
 17. The method of claim 15 whereinthe step of sensing at least one milling operating parameter comprisessensing milling operating parameters of torque, weight on bit, surfaceweight, temperature, pressure, vibration or fluid flow receivedproximate the milling bit bottom hole assembly.